KR20120086207A - Mixture of carbon and silicon carbide and method for the same, and method for manufacturing silicon carbide sintered body - Google Patents

Abstract

PURPOSE: A carbon-silicon carbide mixture, a manufacturing method thereof, a manufacturing method of silicon carbide sintered materials are provided to simplify processes by omitting the addition of a separate sintering aid. CONSTITUTION: A manufacturing method of silicon carbide sintered materials comprises the following steps: forming a mixed raw material by mixing Si sources with carbon sources; heating the mixed raw material(ST10); forming a carbon - silicon carbide mixture which includes residual carbon and silicon carbide; and hot-press forming the carbon - silicon carbide mixture(ST20). In the raw material formation step, a molar ratio of carbon to silicon is 3.1-4. 2-20 parts by weight of the residual carbon based on 100.0 parts by weight of the carbon - silicon carbide mixture. The residual carbon functions as a sintering gradient material.

Description

MIXTURE OF CARBON AND SILICON CARBIDE AND METHOD FOR THE SAME, AND METHOD FOR MANUFACTURING SILICON CARBIDE SINTERED BODY}

The present disclosure relates to a carbon-silicon carbide mixture, a method for producing the same, and a method for producing a silicon carbide sintered body.

Silicon carbide (SiC) is physically and chemically stable, has good heat resistance and thermal conductivity, and is excellent in high temperature stability, high temperature strength and wear resistance. Accordingly, silicon carbide is widely used in the manufacture of high temperature materials, high temperature semiconductors, wear resistant materials, automobile parts, and the like.

Such silicon carbide may be manufactured by a method of mixing a raw material such as a silicon source and a carbon source, followed by heating. The silicon carbide thus produced may be manufactured into a silicon carbide sintered body by a sintering process or the like. When silicon carbide is sintered alone, sintering is not performed well and the density of the sintered compact is low. Therefore, it is common to sinter after mixing and granulating a nonmetal sintering aid with silicon carbide. By the way, the process becomes complicated by the mixing process and granulation process of a nonmetal sintering aid and a silicon carbide, and contaminants may flow in during this process, and the purity of a silicon carbide sintered compact may fall.

The embodiment is intended to provide a method for producing a silicon carbide sintered body that can simplify the process and improve purity and density, and a carbon-silicon carbide mixture and a method for producing the same.

Method for producing a silicon carbide sintered body according to the embodiment, the raw material mixing step of forming a mixed raw material by mixing a silicon source and a carbon source; Heating the mixed raw material to form a carbon-silicon carbide mixture comprising residual carbon and silicon carbide; And a sintering step of hot pressing the carbon-silicon carbide mixture.

In the raw material mixing step, the molar ratio of carbon contained in the carbon source to the silicon contained in the silicon source may be 3.1 to 4.

The residual carbon may be included by 2 to 20 parts by weight based on 100 parts by weight of the carbon-silicon carbide mixture.

In the raw material mixing step, the molar ratio of carbon included in the carbon source to silicon contained in the silicon source may be 3.1 to 3.5.

The residual carbon may be included by 2 to 10 parts by weight based on 100 parts by weight of the carbon-silicon carbide mixture.

The residual carbon may function as a sintering aid.

The silicon carbide may have a beta phase.

The carbon source may include at least one of a solid carbon source and an organic carbon compound.

The solid carbon source may include at least one material selected from the group consisting of graphite, carbon black, carbon nanotubes (CNTs), and fullerenes (C ₆₀ ).

The organic carbon compound is a phenol resin, a franc resin, a xylene resin, a polyimide, a polyurethane, a polyunrethane, a polyvinyl alcohol, a polyacrylonitrile ) And polyvinyl acetate (poly (vinyl acetate)), cellulose (cellulose), sugar, pitch (tar) may include at least one material selected from the group consisting of.

The silicon source may include at least one selected from the group consisting of silica powder, silica sol, silica gel, and quartz powder.

The carbon-silicon carbide mixture according to the embodiment is a carbon-silicon carbide mixture used to prepare a silicon carbide sintered body, and includes 2 to 20 parts by weight of the residual carbon with respect to 100 parts by weight of the carbon-silicon carbide mixture.

The residual carbon may be included by 2 to 10 parts by weight based on 100 parts by weight of the carbon-silicon carbide mixture.

The method for producing a carbon-silicon carbide mixture according to the embodiment relates to a method for producing a carbon-silicon carbide mixture used to prepare a silicon carbide sintered body, and a raw material mixing step of mixing a silicon source and a carbon source to form a mixed raw material ; And heating the mixed raw material to form a carbon-silicon carbide mixture comprising residual carbon and silicon carbide. In the raw material mixing step, the molar ratio of carbon contained in the carbon source to the silicon contained in the silicon source is 3.1 to 4, by 2 to 20 parts by weight of the residual carbon with respect to 100 parts by weight of the carbon-silicon carbide mixture Included.

In the raw material mixing step, the molar ratio of carbon included in the carbon source to silicon contained in the silicon source may be 3.1 to 3.5. The residual carbon may be included by 2 to 10 parts by weight based on 100 parts by weight of the carbon-silicon carbide mixture.

According to the method for producing a silicon carbide sintered body according to the embodiment, the silicon carbide sintered body is formed by sintering a carbon-silicon carbide mixture in which silicon carbide and residual carbon are mixed, so that a step of mixing and granulating by adding a separate sintering aid is omitted. can do. As a result, the process can be simplified, and it is possible to fundamentally prevent contamination that may occur when a separate sintering aid is added.

1 is a process flowchart showing a method of manufacturing a silicon carbide sintered body according to an embodiment.

Hereinafter, a method of manufacturing a silicon carbide sintered body using the carbide-silicon carbide mixture according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a process flowchart showing a method of manufacturing a silicon carbide sintered body according to an embodiment.

Referring to FIG. 1, the method of manufacturing the silicon carbide sintered body according to the present embodiment includes a raw material mixing step ST10, a heating step ST20, and a sintering step ST30. At this time, the carbon-silicon carbide mixture is prepared by the raw material mixing step (ST10) and the heating step (ST20), and then a sintering step (ST30) is performed to hot pressurize the carbon-silicon carbide mixture thus prepared to obtain a silicon carbide sintered body. It can manufacture.

Each step is described in more detail as follows.

In the raw material mixing step (ST10), a silicon source (Si source) and a carbon source (C source) are prepared and mixed to form a mixed raw material.

The silicon source can include various materials that can provide silicon. In one example, the silicon source may comprise silica. Examples of such silicon sources include silica powder, silica sol, silica gel, and quartz powder. However, the embodiment is not limited thereto, and an organosilicon compound including silicon may be used as the silicon source.

The carbon source may comprise a solid carbon source or an organic carbon compound.

Examples of the solid carbon source include graphite, carbon black, carbon nano tube (CNT), and fullerene (C ₆₀ ).

The organic carbon compound includes phenol resin, franc resin, xylene resin, polyimide, polyurethane, polyvinyl alcohol, polyacrylonitrile ), Or polyvinyl acetate (poly (vinyl acetate)) and the like. In addition, cellulose, sugar, pitch, tar and the like can be used.

The silicon source and the carbon source are mixed by a ball mill, an attrition mill, a 3 roll mill, or the like to recover the mixed powder. The mixed powder can be caught and recovered by a sieve. When the organic carbon compound is used, the recovered mixed powder can be dried in a spray dryer or the like.

Subsequently, in the heating step ST20, the mixed powder (that is, mixed raw materials) is heated. Then, silicon carbide is formed by the overall scheme of Scheme 3 by the steps of Schemes 1 and 2 below.

[Reaction Scheme 1]

SiO ₂ (s) + C (s)-> SiO (g) + CO (g)

Scheme 2

SiO (g) + 2C (s)-> SiC (s) + CO (g)

Scheme 3

SiO ₂ (s) + 3C (s)-> SiC (s) + 2CO (g)

The heating temperature may be 1300 ° C. or more so that the reaction as described above may occur smoothly. At this time, the silicon carbide produced at a heating temperature of 1400 to 1800 ° C. may have a beta phase which is a low temperature stable phase. The beta phase is made of fine particles can improve the strength and the like of silicon carbide. However, the embodiment is not limited thereto. Therefore, it is a matter of course that the silicon carbide may have an alpha phase which is a high temperature stable phase by allowing the heating temperature to exceed 1800 ° C.

The heating time in the heating step ST20 may be 30 minutes or more, for example, 1 hour to 7 hours. However, the embodiment is not limited thereto, and the heating time may be selected to be suitable for forming silicon carbide.

This heating step ST20 may be performed in an inert atmosphere or vacuum of high purity (for example, 5N or more). This is to prevent unwanted side reactions from occurring during the synthesis of silicon carbide. However, the present invention is not limited thereto, and heating may be performed in various atmospheres.

In the present embodiment, the mole ratio of carbon included in the carbon source to silicon contained in the silicon source (hereinafter referred to as “mole ratio of carbon to silicon”) in the raw material mixing step (ST10) is 3.1 to 4, and the heating step Carbon remains after (ST20) to form a carbon-silicon carbide mixture. This will be described in more detail later.

Subsequently, in the sintering step ST30, the manufactured carbon-silicon carbide mixture is sintered to form a silicon carbide sintered body having a desired shape. This sintering step ST30 may be performed in a hot press sintering apparatus such as a hot press. For example, sintering may be performed by pressing at a pressure of 10 to 50 MPa at a temperature of 2100 to 2400 ° C. The gas atmosphere may be an inert gas atmosphere or a vacuum. However, the embodiment is not limited thereto, and sintering may be performed at various temperatures, pressures, and gas atmospheres.

In this embodiment, the carbon remaining in the carbon-silicon carbide mixture serves as a sintering aid, and it is not necessary to separately add a nonmetal sintering aid to mix and granulate it. Thereby, the process can be simplified and contamination by the nonmetal sintering aid can be prevented at the source. This will be described in more detail as follows.

Considering only the reaction schemes 1 to 3 described above, the molar ratio of carbon to silicon is preferably 3. However, in consideration of the fact that SiO gas is formed and volatilized so that a part of silicon does not participate in the reaction as in Scheme 1, the molar ratio of carbon to silicon is generally less than three.

In the present embodiment, on the contrary, the molar ratio of carbon to silicon is greater than 3 to form a carbon-silicon carbide mixture having a predetermined amount or more of residual carbon together with silicon carbide after the heating step ST20. The residual carbon is used as a sintering aid in the step of hot pressing, so that the silicon carbide sintered body can have a high density.

At this time, as described above, the molar ratio of carbon to silicon is 3.1 to 4, so that the amount of residual carbon acting as a sintering aid can be appropriately adjusted. For example, when the molar ratio of carbon to silicon is 3.1 to 4, the residual carbon may be included by 2 to 20 parts by weight based on 100 parts by weight of the carbon-silicon carbide mixture. When the molar ratio is 4 or more, the residual carbon is more than 20 parts by weight, and carbon remains after the sintering step, so that the density of the silicon carbide sintered body may be rather reduced. If the molar ratio is less than 3.1, the residual carbon may not fully serve as the sintering aid at less than 2 parts by weight.

At this time, the molar ratio of carbon to silicon may be 3.1 to 3.5, so that 2 to 10 parts by weight of residual carbon may be included with respect to 100 parts by weight of the carbon-silicon carbide mixture. Since the density of the silicon carbide sintered body is no longer increased when the residual carbon is about 10 parts by weight or more, the residual carbon may be 10 parts by weight or less, thereby maximizing the amount of silicon carbide and maximizing the density improving effect.

Hereinafter, the present invention will be described in more detail through the manufacturing method of the silicon carbide sintered body according to the production examples and the comparative examples. These preparations are merely presented by way of example in order to explain the invention in more detail. Therefore, the present invention is not limited to these preparation examples.

Manufacturing example  One

The silica powder and carbon black were mixed by ball mill. At this time, the molar ratio of carbon contained in carbon black to silicon contained in silica powder was 3.2. The mixed powder was collected using a sieve, placed in an argon atmosphere graphite furnace, and heated at 1800 ° C. for 3 hours to prepare a carbon-silicon carbide mixture. At this time, 2 parts by weight of residual carbon was included based on 100 parts by weight of the carbon-silicon carbide mixture.

Subsequently, the raw material mixed in the hot pressurizing sintering apparatus was charged, and it hot-pressed at the pressure of 40 Mpa at the temperature of 2200 degreeC, and the silicon carbide sintered compact was formed.

Manufacturing example  2

A silicon carbide sintered body was formed in the same manner as in Production Example 1, except that the molar ratio of carbon to silicon was 3.3 and the residual carbon was included by 6 parts by weight based on 100 parts by weight of the carbon-silicon carbide mixture.

Manufacturing example  3

A silicon carbide sintered body was formed in the same manner as in Production Example 1, except that the molar ratio of carbon to silicon was 3.4 and the residual carbon was included by 10 parts by weight with respect to 100 parts by weight of the carbon-silicon carbide mixture.

Manufacturing example  4

A silicon carbide sintered body was formed in the same manner as in Production Example 1, except that the molar ratio of carbon to silicon was 3.5 and 15 parts by weight of residual carbon was included based on 100 parts by weight of the carbon-silicon carbide mixture.

Comparative example  One

A silicon carbide sintered body was formed in the same manner as in Production Example 1, except that the molar ratio of carbon to silicon was 2.8 and the residual carbon was included by 1 part by weight based on 100 parts by weight of the carbon-silicon carbide mixture.

Comparative example  2

A silicon carbide sintered body was formed in the same manner as in Production Example 1, except that the molar ratio of carbon to silicon was 4.2 and 25 parts by weight of residual carbon was included with respect to 100 parts by weight of the carbon-silicon carbide mixture.

The density of the silicon carbide sintered bodies prepared in Preparation Examples 1 to 4 and Comparative Examples 1 and 2 was measured and shown in Table 1 below.

Density [g / cm ³ ] Preparation Example 1 2.4 Production Example 2 3.0 Production Example 3 3.14 Production Example 4 3.16 Comparative Example 1 2.4 Comparative Example 2 2.3

Referring to Table 1, it can be seen that the density of the silicon carbide sintered body according to Production Examples 1 to 4 is superior to Comparative Examples 1 and 2. Therefore, it can be seen that the density of the silicon carbide sintered body can be improved by using a carbon-silicon carbide mixture containing 2 to 20 parts by weight of residual carbon.

In addition, it can be seen that the density of Production Example 3 using the carbon-silicon carbide mixture containing 10 parts by weight of residual carbon and Production Example 4 using the carbon-silicon carbide mixture containing 15 parts by weight of residual carbon are similar. From this, when the residual carbon is 10 parts by weight or more, it can be seen that it is preferable to include the residual carbon by 2 to 10 parts by weight since the density increase range is not large.

The features, structures, effects and the like described in the foregoing embodiments are included in at least one embodiment of the present invention and are not necessarily limited to one embodiment. In addition, the features, structures, effects, and the like illustrated in the embodiments may be combined or modified with respect to other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

In addition, the above description has been made with reference to the embodiments, which are merely examples and are not intended to limit the invention. It will be appreciated that various modifications and applications are possible. For example, each component specifically shown in the embodiments may be modified and implemented. It is to be understood that the present invention may be embodied in many other specific forms without departing from the spirit or essential characteristics thereof.

Claims (15)

A raw material mixing step of forming a mixed raw material by mixing the silicon source and the carbon source;
Heating the mixed raw material to form a carbon-silicon carbide mixture comprising residual carbon and silicon carbide; And
Sintering step of hot pressing the carbon-silicon carbide mixture
Method for producing a silicon carbide sintered body comprising a. The method of claim 1,
The method of producing a silicon carbide sintered body in the raw material mixing step, the molar ratio of carbon contained in the carbon source to the silicon contained in the silicon source is 3.1 to 4. The method of claim 1,
A method for producing a silicon carbide sintered body containing 2 to 20 parts by weight of the residual carbon based on 100 parts by weight of the carbon-silicon carbide mixture. The method of claim 2,
In the raw material mixing step, the silicon carbide sintered body manufacturing method of the molar ratio of carbon contained in the carbon source to the silicon contained in the silicon source is 3.1 to 3.5. The method of claim 4, wherein
A method for producing a silicon carbide sintered body containing 2 to 10 parts by weight of the residual carbon based on 100 parts by weight of the carbon-silicon carbide mixture. The method of claim 1,
A method for producing a silicon carbide sintered compact in which the residual carbon functions as a sintering aid. The method of claim 6,
A method for producing a silicon carbide sintered body in which the silicon carbide has a beta phase. The method of claim 1,
A method for producing a silicon carbide sintered compact in which the carbon source comprises at least one of a solid carbon source and an organic carbon compound. The method of claim 8,
Manufacture of silicon carbide sintered body comprising at least one material selected from the group consisting of graphite, carbon black, carbon nanotube (CNT) and fullerene (C ₆₀ ) Way. The method of claim 8,
The organic carbon compound is a phenol resin, a franc resin, a xylene resin, a polyimide, a polyurethane, a polyunrethane, a polyvinyl alcohol, a polyacrylonitrile ) And polyvinyl acetate (poly (vinyl acetate)), cellulose (cellulose), sugar, pitch (tar) and at least one material selected from the group consisting of tar (tar). The method of claim 1,
And the silicon source comprises at least one selected from the group consisting of silica powder, silica sol, silica gel, and quartz powder. As a carbon-silicon carbide mixture used to prepare a silicon carbide sintered body,
A carbon-silicon carbide mixture containing 2 to 20 parts by weight of the residual carbon relative to 100 parts by weight of the carbon-silicon carbide mixture. The method of claim 12,
A carbon-silicon carbide mixture containing 2 to 10 parts by weight of the residual carbon relative to 100 parts by weight of the carbon-silicon carbide mixture. In the method for producing a carbon-silicon carbide mixture used to prepare a silicon carbide sintered body,
A raw material mixing step of forming a mixed raw material by mixing the silicon source and the carbon source; And
Heating the mixed raw material to form a carbon-silicon carbide mixture comprising residual carbon and silicon carbide;
Including,
In the raw material mixing step, the molar ratio of carbon contained in the carbon source to silicon contained in the silicon source is 3.1 to 4,
Method for producing a carbon-silicon carbide mixture containing 2 to 20 parts by weight of the residual carbon relative to 100 parts by weight of the carbon-silicon carbide mixture. 15. The method of claim 14,
In the raw material mixing step, the molar ratio of carbon contained in the carbon source to silicon contained in the silicon source is 3.1 to 3.5,
Method for producing a carbon-silicon carbide mixture containing 2 to 10 parts by weight of the residual carbon with respect to 100 parts by weight of the carbon-silicon carbide mixture.

Images